A number of Tory MPs have promised to back a fresh Labour bid to lower the voting age to 16, the shadow youth minister has said.
Cat Smith said she was "optimistic" that a private member's bill led by Labour MP Jim McMahon had a good chance of becoming law.
She was speaking to BuzzFeed News at a fringe event at the Labour conference in Brighton on Tuesday, where she urged students to lobby their MP to back the bill at its second reading on 3 November.
McMahon's bill would lower the voting age from 18 to 16 for UK elections, and would ensure young people were educated in "citizenship and the constitution".
Theresa May, the prime minister, made clear earlier this year that she did not believe the voting age should be lowered, saying: "You have to pick a point at which you think it is right for the voting age to be. I continue to think it is right for it to be 18."
But Labour, the Liberal Democrats, the Greens, and the SNP all back votes at 16. The voting age was lowered to 16 for the 2014 Scottish independence referendum.
Smith said: "I actually am very optimistic about it because we have had Conservative MPs tell me and other Labour MPs that they will be supporting votes at 16.
"I'm not going to name names just in case they’re not entirely public about it, and I don’t want to upset any chances of getting this private member's bill through – but I am quite confident.
"Although Theresa May is opposed to votes at 16, I think she will find that not all her MPs will vote with her on this issue. And even if they absent themselves, it might be all we need in the current parliamentary arithmetic to get the bill through."
McMahon's bill is formally backed by a string of MPs from all parties, including Tory MP Sir Peter Bottomley. A long-term supporter of votes at 16, Bottomley signed an early day motion tabled by Green MP Caroline Lucas in June that stated that "the UK's 1.5 million 16 and 17-year-olds are as knowledgeable and competent to vote as other young adults".